Python的Flask开发框架简单上手笔记

2024-03-25 17:21:03 393

最简单的helloworld

#!/usr/bin/envpython
#encoding:utf-8

fromflaskimportFlask
app=Flask(__name__)

@app.route('/')
defindex():
return'helloworld'

if__name__=='__main__':
app.run(debug=True)
#app.run(host='127.0.0.1',port=8000)

之后，访问http://localhost:5000

支持post/get提交

@app.route('/',methods=['GET','POST'])

多个url指向

@app.route('/')
@app.route('/index')

不管post/get使用统一的接收

fromflaskimportrequest
args=request.argsifrequest.method=='GET'elserequest.form
a=args.get('a','default')

处理json请求
request的header中

"Content-Type":"application/json"

处理时:

data=request.get_json(silent=False)

获取post提交中的checkbox

{%forpageinpages%}
<tr><td><inputtype=checkboxname=do_deletevalue="{{page['id']}}"></td><td>
{%endfor%}

page_ids=request.form.getlist("do_delete")

使用url中的参数

@app.route('/query/<qid>/')
defquery(qid):
pass

在request开始结束dosomething
一般可以处理数据库连接等等

fromflaskimportg

app=.....

@app.before_request
defbefore_request():
g.session=create_session()

@app.teardown_request
defteardown_request(exception):
g.session.close()

注册Jinja2模板中使用的过滤器

@app.template_filter('reverse')
defreverse_filter(s):
returns[::-1]

或者

defreverse_filter(s):
returns[::-1]
app.jinja_env.filters['reverse']=reverse_filter

可以这么用

defa():...
defb():...

FIL={'a':a,'b':b}
app.jinja_env.filters.update(FIL)

注册Jinja2模板中使用的全局变量

JINJA2_GLOBALS={'MEDIA_PREFIX':'/media/'}
app.jinja_env.globals.update(JINJA2_GLOBALS)

定义应用使用的template和static目录

app=Flask(__name__,template_folder=settings.TEMPLATE_FOLDER,static_folder=settings.STATIC_PATH)

使用Blueprint

fromflaskimportBlueprint
bp_test=Blueprint('test',__name__)
#bp_test=Blueprint('test',__name__,url_prefix='/abc')

@bp_test.route('/')

--------
fromxxximportbp_test

app=Flask(__name__)
app.register_blueprint(bp_test)

实例:

bp_video=Blueprint('video',__name__,url_prefix='/kw_news/video')
@bp_video.route('/search/category/',methods=['POST','GET'])
#注意这种情况下Blueprint中url_prefix不能以'/'结尾,否则404

使用session
包装cookie实现的，没有sessionid

app.secret_key='PS#yio`%_!((f_or(%)))s'

然后

fromflaskimportsession

session['somekey']=1
session.pop('logged_in',None)

session.clear()

#过期时间,通过cookie实现的
fromdatetimeimporttimedelta
session.permanent=True
app.permanent_session_lifetime=timedelta(minutes=5)

反向路由

fromflaskimporturl_for,render_template

@app.route("/")
defhome():
login_uri=url_for("login",next=url_for("home"))
returnrender_template("home.html",**locals())

上传文件

<formaction="/image/upload/"method="post"enctype="multipart/form-data">
<inputtype="file"name="upload"/>

接收

f=request.files.get('upload')
img_data=f.read()

直接返回某个文件

returnsend_file(settings.TEMPLATE_FOLDER+'tweet/tweet_list.html')

请求重定向

flask.redirect(location,code=302)theredirectstatuscode.defaultsto302.Supportedcodesare301,302,303,305,and307.300isnotsupported.

@app.route('/')
defhello():
returnredirect(url_for('foo'))

@app.route('/foo')
deffoo():
return'HelloFoo!'

获取用户真实ip
从request.headers获取

real_ip=request.headers.get('X-Real-Ip',request.remote_addr)
或者,使用werkzeug的middleware文档

fromwerkzeug.contrib.fixersimportProxyFix
app.wsgi_app=ProxyFix(app.wsgi_app)
returnjson&jsonp
importjson
fromflaskimportjsonify,Response,json

data=[]#orothers
returnjsonify(ok=True,data=data)

jsonp_callback=request.args.get('callback','')
ifjsonp_callback:
returnResponse(
"%s(%s);"%(jsonp_callback,json.dumps({'ok':True,'data':data})),
mimetype="text/javascript"
)
returnok_jsonify(data)

配置读取方法

#createourlittleapplication:)
app=Flask(__name__)

#Loaddefaultconfigandoverrideconfigfromanenvironmentvariable
app.config.update(dict(
DATABASE='/tmp/flaskr.db',
DEBUG=True,
SECRET_KEY='developmentkey',
USERNAME='admin',
PASSWORD='default'
))
app.config.from_envvar('FLASKR_SETTINGS',silent=True)


------------------
#configuration
DATABASE='/tmp/minitwit.db'
PER_PAGE=30
DEBUG=True
SECRET_KEY='developmentkey'

#createourlittleapplication:)
app=Flask(__name__)
app.config.from_object(__name__)
app.config.from_envvar('MINITWIT_SETTINGS',silent=True)

几个不常用的方法

fromflaskimportabort,flash

abort
ifnotsession.get('logged_in'):
abort(401)

flash
flash('Newentrywassuccessfullyposted')

异步调用
想在flask的一个请求中处理异步,除了使用消息系统,可以用简单的线程处理

fromthreadingimportThread

defasync(f):
defwrapper(*args,**kwargs):
thr=Thread(target=f,args=args,kwargs=kwargs)
thr.start()
returnwrapper

@async
defdosomething(call_args):
printcall_args


inarequesthandler,call`dosomething`
errorhandler
@app.errorhandler(404)
defnot_found_error(error):
returnrender_template('404.html'),404

@app.errorhandler(500)
definternal_error(error):
db.session.rollback()
returnrender_template('500.html'),500

项目配置
1.直接

app.config['HOST']='xxx.a.com'
printapp.config.get('HOST')

2.环境变量

exportMyAppConfig=/path/to/settings.cfg
app.config.from_envvar('MyAppConfig')

3.对象

classConfig(object):
DEBUG=False
TESTING=False
DATABASE_URI='sqlite://:memory:'

classProductionConfig(Config):
DATABASE_URI='mysql://user@localhost/foo'

app.config.from_object(ProductionConfig)
printapp.config.get('DATABASE_URI')#mysql://user@localhost/foo

4.文件

#default_config.py
HOST='localhost'
PORT=5000
DEBUG=True

app.config.from_pyfile('default_config.py')

EG.一个create_app方法

fromflaskimportFlask,g

defcreate_app(debug=settings.DEBUG):
app=Flask(__name__,
template_folder=settings.TEMPLATE_FOLDER,
static_folder=settings.STATIC_FOLDER)

app.register_blueprint(bp_test)

app.jinja_env.globals.update(JINJA2_GLOBALS)
app.jinja_env.filters.update(JINJA2_FILTERS)

app.secret_key='PO+_)(*&678OUIJKKO#%_!(((%)))'

@app.before_request
defbefore_request():
g.xxx=...#dosomething

@app.teardown_request
defteardown_request(exception):
g.xxx=...#dosomething

returnapp

app=create_app(settings.DEBUG)
host=settings.SERVER_IP
port=settings.SERVER_PORT
app.run(host=host,port=port)
changelog:

2013-09-09create
2014-10-25update

Python的Flask开发框架简单上手笔记

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